Delta-wing aircraft

ABSTRACT

A delta-wing aircraft comprises a pair of auxiliary wings pivotably mounted forwardly of the leading edge of the delta-wing from a deployed position at lower speeds wherein they increase lift and also act as horizontal stabilizers, to a retracted dragdecreasing position at cruising speeds. In one described embodiment, the auxiliary wings are pivotable about a vertical axis of the aircraft from a deployed position wherein their leading edges are about 90* to the longitudinal axis of the aircraft, to a retracted position wherein they form the apex of the delta-wing; in both positions, the mean aerodynamic chord of the auxiliary wings is aligned with that of the delta-wing. In a second described embodiment, the pair of auxiliary wings are pivoted about a horizontal axis of the aircraft, from a deployed position substantially perpendicular to the longitudinal axis of the aircraft, to a retracted position substantially flush with the aircraft fuselage.

United States Patent 1 Bouchnik DELTA-WING AIRCRAFT [76] Inventor:Joseph Bouchnik, Mashay Mismeret,

Gush Tel-Mond, Israel.

[22] Filed: Oct. 12, 1970 [21] Appl. No.: 79,740

[30] Foreign Application Priority Data Oct. 14,1969 Italy ..33l85/69[52] U.S. Cl. 244/43 [51] Int. Cl. B64c 3/56 [58] Field of Search;244/43, 49, 42, 41,

[56] References Cited UNITED STATES PATENTS 2,430,793 11/1947 Wells244/87- 2,941,752 6/1960 Gluhareff 244/46 3,478,989 11/1969 Bielefeldt244/43 3,104,079 9/1963 Phillips 244/43 3,104,082 9/1963 Polhamus 244/432,793,826 5/1957 Fieldler 244/43 FOREIGN PATENTS 0R APPLICATIONS1,083,557 11/1955 France 244/46 [111 3,738,595 June 12, 1973 PrimaryExaminer-Duane A. Reger Assistant Examiner-Carl A. RutledgeAttorney-Benjamin J. Barish 57] ABSTRACT A delta-wing aircraft comprisesa pair of auxiliary wings pivotably mounted forwardly of the leadingedge of the delta-wing from a deployed position at lower speeds whereinthey increase lift and also act as horizontal stabilizers, to aretracted drag-decreasing posi tion at cruising speeds. In one describedembodiment, the auxiliary wings are pivotable about a vertical axis ofthe aircraft from a deployed position wherein their leading edges areabout 90 to the longitudinal axis of the aircraft, to a retractedposition wherein they form the apex of the delta-wing; in bothpositions, the mean aerodynamic chord of the auxiliary wings is alignedwith that of the delta-wing. In a second described embodiment, the pairof auxiliary wings are pivoted about a horizontal axis of the aircraft,from a deployed position substantially perpendicular to the longitudinalaxis of the aircraft, to a retracted position substantially flush withthe aircraft fuselage,

4 Claims, 10 Drawing Figures Patented June 12,1973 3,738,595

2 Sheets-Shut 1 INVENTOR JOSEPH BOUCHNIK ATTORNEY Patented June 12, 19733,738,595

2 Shoots-Shoot B FIG.6

FIG. 10

H2 RO CG I INVENTOR i 1 1 h r1254 28 w v I I BY A TTORNEV DELTA-WINGAIRCRAFT BACKGROUND OF THE INVENTION and landing the entire wing ismoved forwardly so as to provide a larger lift, and at cruising speedthe wings are retracted forming a delta-shaped wing. The Swedish Viggen37 is a delta-wing aircraft provided with flaps used for increasing thelift during take-off and landing,

' and including a fixed canard or stabilizer located at the forward partof the plane which is advantageous during take-off and landing butdisadvantageous at cruising speeds. A similar arrangement has beenproposed for the B70.

SUMMARY OF THE PRESENT INVENTION According to a broad aspectof thepresent invention, there is provided a delta-wing aircraft characterizedin that it includes a pair of canard control surfaces or auxiliary wingspivotably mounted forwardly of the leading edge of the delta-wing from adeployed position at lower speeds wherein they increase lift and alsoact as horizontal stabilizers, to a retracted drag-decreasing positionat cruising speeds. 1

In a preferred embodiment of the invention described below, called thevariable-delta configuration, the auxiliary wings are mounted forpivoting about a vertical axis of the root of the main delta wing of theaircraft, such that the mean aerodynamic chord of the auxiliary wings isin alignment with that of the deltawing in both the deployed andretracted positions of the auxiliary wings, and that pivoting them inthe direction of the deployed position increases the total surface areaaspect ratio, camber and effective thickness of the main delta wing andauxiliary wings, and the angle of their leading edges to the directionof flight. In this embodiment it is possible to vary the position of theauxiliary wings to any one of a plurality of intermediate positionsbetween the fully deployed position and the fully retracted position,thus providing for intermediate values of additional lift andstabilization whenever required.

A second embodiment of the invention is also described wherein the pairof canard control surfaces are mounted for pivoting about a horizontalaxis parallel to the longitudinal axis of the aircraft. In thisembodiment, they are mounted for pivoting from a deployed positionsubstantially perpendicular to the longitudinal axis of the aircraft, toa retracted position substantially flush with the aircraft fuselage.

Further features and advantages of the invention will be apparent fromthe description below.

BRIEF DESCRIPTION OF THE DRAWINGS.

The invention is herein described, somewhat diagrammatically and by wayof example only, with reference to the accompanying drawings, wherein:

FIG. I is a side elevational view of a delta-wing aircraft constructedwith a pair of auxiliary wings pivotably mounted about a vertical axisin accordance with one embodiment of the present invention;

FIG. 2 is a plan'view of the aircraft of FIG. I, the auxiliary wingsbeing shown in their retracted position in full lines, and in theirdeployed position in broken line;

FIG. 3 is a front elevational view of the aircraft of FIGS. 1 and 2, theauxiliary wings. beingshown in their deployed position;

FIG. 4 is a schematic, non-scale diagram illustrating the main verticalforces applicable to the airfoil section of the aircraft of FIGS. 1-3,at the mean aerodynamic chord thereof, with the auxiliary wings in theirretracted position;

FIG. 5 is a diagram similar to that of FIG. 4, but showing the mainvertical forces applicable when the auxiliary wings are in theirdeployed position;

FIG. 6 is a side elevational view of adelta-wing aircraft constructed inaccordacne with a second embodiment of the invention, with a pair ofauxiliary wings pivotably mounted about a horizontal axis parallel tothe longitudinal axis of the aircraft; FIGS. 7 and 8 are plan andfront'elevational views, respectively, of the aircraft of FIG. 6,illustrating the auxiliary wings in their deployed position; and

FIGS. 9 and 10 are diagrams similar to those of FIGS. i

4 and 5 but showing the vertical forces applicable to the aircraft ofFIGS. 6 8 when the auxiliary wings are in their retracted and deployedpositions, respectively.

DESCRIPTION OF THE EMBODIMENT OF FIGS.

The aircraft 2 illustrated in FIGS. l-3 is termed a variable-deltaconfiguration. It comprises a fuselage 4, a fixed delta-wing 6,air-intakes 7, rear flaps 8 including ailerons 8' for roll control andelevons 8" for pitch control at high speeds, directional rudder 9, and apair of auxiliary wings 10 pivotably mounted forwardly of the leadingedge of the delta-wing 6, between it and the air-intakes 7. In thisembodiment, the forward stabilizers 10 are mounted for pivoting about avertical axis 12 at the root of the main delta-wing 6 of the aircraftfrom the deployed position 10a shown in broken lines in FIG. 2, to theretracted position 10b shown in full lines in FIG. 2, or to any one of anumber of intermediate positions. Any suitable power means, such ashydraulic system, provided on the aircraft may be used for actuating theauxiliary wings 10 as schematically indicated by the block 14 in FIG. 2.

The auxiliary wings 10 are so disposed that their mean aerodynamic chordA is in alignment with the mean aerodynamic chord B of the delta-wing inthe deployed and retracted positions, as well as in all intermediatepositions. They carry control flaps 16 at their trailing edges, whichflaps may also include spoilers (not shown), for roll-axis control.

The deployed position 10a of the auxiliary wings is used for low speeds,such as at take-off or landing, and also at very high altitudes; whereasthe retracted position 10b is used for normal cruising speed.

When the auxiliary wings 10 are moved to their deployed position, thetotal wing surface area and aspect ratio are increased; also the angleof incidence of their leading edges to the direction of flight (i.e.longitudinal axis L, FIG. 2) is increased and their chord is decreased,thereby producing an increase in the camber and thickness of theauxiliary wings and delta-wing profiles. This produces an increase inthe lift coefficient, which is greatest when the leading edges of theauxiliary wings are at right angles to the direction of flight.

Accordingly, the fully deployed position, of the auxiliary wings isabout 90 to the longitudinal axis L of the aircraft, but it may beslightly more in some applications, for example, up to about 105, toprovide longitudinal stability control.

In the retracted position b of the auxiliary wings 10, a part of theirsurface area overlies (or underlies) the front part of the delta-wingand may also enter the fuselage, whereby the effective surface area ofthe auxiliary wings is substantially reduced, e.g. about twothirds, ascompared to the deployed position. The auxiliary wings in the retractedposition form the apex of the delta-wing, and preferably have a sharpersweepback than the delta-wing proper. For example, in an aircraft havinga delta-wing of about 60 sweep-back (i.e. forming an angle of 30 withrespect to the aircraft longitudinal axis L), the leading edge of theauxiliary wings 10 in their fully retracted position could have about a10 sharper sweep-back (i.e. a 70 sweep-back). Preferably the sweep-backof the deltawing may vary from 6065; and that of the apex formed by theretracted auxiliary wings may vary from 70-85.

It will thus be seen that deploying the auxiliary wings increases lift.It also has a horizontal stabilizing effect against pitch movements.Thus, when the auxiliary wings are forwardly deployed, the aerodynamiccenter of the delta-wing proper tends to move aft, increasing thedistance from the aircraft center of gravity, and thereby tendingtoproduce a nose-down movement. The auxiliary wings have an independentaerodynamic center which is forward of the center of gravity, andtherefore the lift force of the auxiliary wings tends to compensate thenose-down movement of the deltawing.

FIG. 4 illustrates, schematically and in non-scale, the vertical forcesapplicable to the airfoil section of both the delta-wing and theauxiliary wings when the latter are in their retracted position, theplane flying at high speed with a small angle of flight (a). Theresultant lift force R1 applicable to the aerodynamic center AC of thewing is that produced by both the delta-wing 6 and auxiliary wings 10.The latter is the apex of the deltawing, and therefore its lift force isnot shown separately. The resultant gravity force R2 is applicable atthe center of gravity CG of the aircraft, which is slightly forward ofthe aerodynamic center AC. The characteristics of the aircraft at highspeed, with the auxiliary wings retracted, thus resemble those of a puredeltawing aircraft.

FIG. 5 illustrates the vertical forces applicable upon landing ortake-off with the auxiliary wings in their deployed positions, and witha maximum angle of attack (a) of about The resultant delta-wing liftforce, indicated by arrow R10 at the aerodynamic center AC of theaircraft, comprises force Fl produced by the delta-wing 6, force F2produced by the delta-wing flaps 8, force F3 produced by the deployedauxiliary wings l0, and force F4 produced by flaps 16. The latter twoforces are at the independent aerodynamic center AC of the auxiliarywings. The additional force resulting from the increase in camber andthickness of the profiles of the auxiliary wings and of the delta wingsis indicated by force F5. The resultant gravity force is indicated byarrow R11 passing through the center of gravity CG of the aircraft,which is slightly forward. of the aerodynamic center AC of the aircraft,but behind the aerodynamic center AC vof the deployed auxiliary wings.

DESCRIPTION OF THE EMBODIMENT OF FIGS. 6-10.

The aircraft 22 of FIGS. 6-10 comprises a fuselage 24, a delta-wing 26,air-intakes 27, rear flaps 28 including ailerons 28 for roll control andelevons 28" for pitch control at high speeds, directional rudder 29, anda pair of auxiliary wings 30 pivotably mounted forwardly of the leadingedge of the delta-wing 26 between it and the air-intakes 27. Asdistinguished from the variable-delta configuration of FIGS. l-5, theauxiliary wings 30 in the embodiment of FIGS. 6-10 are mounted forpivoting about a horizontal axis 32 parallel to the longitudinal axis ofthe aircraft, from the deployed position 30a shown in full lines in FIG.8 to the retracted position 30b shown in broken lines in FIG. 8. Anysuitable power means, such as a hydraulic system, provided on theaircraft may be used for actuating the auxiliary wings 30 asschematically indicated by the block 34 in FIG. 7. I

The auxiliary wings 30 are so disposed that their mean aerodynamic cordA is in alignment with the mean aerodynamic cord B of the delta-wing inthe deployed position of the auxiliary wings as shown in FIG. 7. Theauxiliary wings are moved against and flush with the fuselage, so as tobe ineffective, in their retracted position. As in the embodiment ofFIGS. l-5, auxiliary wings 30 are also provides with flaps 36 at theirtrailing edges which may include spoilers (notshown).

The auxiliary wings 30 are moved to their deployed position 30a attake-off or landing, and also at very high altitudes, when theadditional lift produced by them is required. During normal supersoniccruising of the aircraft, the auxiliary wings are pivoted downwardly, asshown by arrow F in FIG. 8, to their retracted position 30b flushagainst the fuselage 24 to minimize drag. It is desirable to providerecesses in the fuselage for receiving the auxiliary wings in theirretracted position.

The diagram of FIG. 9 illustrates, schematically and in non-scale, theresultant vertical forces applicable to the aircraft when the auxiliarywings are in their retracted position, the plane flying at high speedwith a small angle of flight (a). Thus, the auxiliary wings 30 in thisposition are ineffective to produce any lift, and therefore theresultant lift force R20 is indicated as that produced by the delta-wing26 alone applied to the aerodynamic center AC, as in a pure delta-wingaircraft. The gravity force is indicated by arrow R21 applied to thecenter of gravity CG of the aircraft, which is slightly forward of theaerodynamic center AC.

FIG. 10 illustrates the vertical forces applicable when the auxiliarywings are in their deployed position, and with a maximum angle of attack(a') of about 15. Thus, the resultant lift force R30 applied to theaerodynamic center AC of the aircraft is the resultant of force F10produced by the delta-wing 26, force Fll produced by the wing flaps 28,force F12 produced by the deployed auxiliary wings 30, and force F13produced by flaps 36. The gravity force is indicated by the arrow R31passing through the center of gravity CG of the aircraft, again slightlyforward of AC but behind AC, the latter being the independentaerodynamic center of the auxiliary wings.

As indicated earlier, the area of the auxiliary wings in bothembodiments can be varied within wide limits in accordance with the sizeand required characteristics of the particular aircraft, the latter alsodetermining the surface area of the delta-wing proper, as known per se.The size of such auxiliary wings will also depend upon their position inthe aircraft. Thus, the further forward they are mounted the smallerwill be their surface area; and the further aft, the larger will betheir surface area. Usually the surface area of the auxiliary wings willconstitute about l0-20 percent of the surface area of the delta-wing.

Preferably, the forward auxiliary wings are located between theair-intakes and the delta-wing, but when the engines are located in themain delta-wing, they may be located in front of the air-intakes.

Many variations, modifications and other applications of the illustratedembodiments will be apparent. What is claimed is:

1. An aircraft comprising a fuselage and a main delta wing fixed to thefuselage, characterized in that the aircraft includes a pair ofauxiliary wings each pivotably mounted about a vertical axis at. theforward juncture of the main delta wing with the fuselage, saidauxiliary wings being pivotable from a deployed position at lower speedsto a retracted position at cruising speed and constituting the apex ofthe main delta wing when in said retracted position, the meanaerodynamic chord of said auxiliary wings being in alignment with thatof the main delta wing in both the deployed and retracted positions ofsaid auxiliary wings, said auxiliary wings when in said deployedposition, increasing the total surface area, aspect ratio, camber, andeffective thickness tion so that their leading edges form an angle of atleast about 90 to the longitudinal axis of the aircraft. =t=

1. An aircraft comprising a fuselage and a main delta wing fixed to thefuselage, characterized in that the aircraft includes a pair ofauxiliary wings each pivotably mounted about a vertical axis at theforward juncture of the main delta wing with the fuselage, saidauxiliary wings being pivotable from a deployed position at lower speedsto a retracted position at cruising speed and constituting the apex ofthe main delta wing when in said retracted position, the meanaerodynamic chord of said auxiliary wings being in alignment with thatof the main delta wing in both the deployed and retracted positions ofsaid auxiliary wings, said auxiliary wings when in said deployedposition, increasing the total surface area, aspect ratio, camber, andeffective thickness of the total wing surface area including the maindelta wing and the auxiliary wings, thereby increasing lift andhorizontal stabilization of the aircraft.
 2. An aircraft as defined inclaim 1, wherein the surface area of said pair of auxiliary wingsconstitute about 10-20 percent of the surface area of the main deltawing.
 3. The aircraft as defined in claim 1, wherein said auxiliarywings carry control flaps at their trailing edges.
 4. The aircraft asdefined in claim 1, wherein said auxiliary wings may be pivoted to afully deployed position so that their leading edges form an angle of atleast about 90* to the longitudinal axis of the aircraft.